Is Driving High on Marijuana Safer Than Driving Drunk?

For decades, marijuana advocates have argued that pot has a significantly different effect on driving ability than alcohol. But if you take the word of one auto insurance company, stoned is actually the safest way to drive.

4AutoinsuranceQuote.org is making that case based on years’ worth of scientific studies, including some from the US National Highway Transportation Safety Administration that found motorists under the influence of marijuana tended to drive slower and have accident responsibility rates lower than those of drug-free drivers. But the company’s interpretation of the data doesn’t tell the whole story.

“There is evidence that cannabis causes changes in performance, and some of these changes may make you less likely to have an accident,” said Paul Armentano, Deputy Director of NORML, The National Organization for the Reform of Marijuana Laws. “For instance, you’re less likely to change lanes, so you’re less likely to have accidents occurring as a result of that. But that does not necessarily make you a safer driver. For instance, we see performance changes in braking latency, and there’s also some evidence of impairment of peripheral vision.”

Paul Armentano, Deputy Director of NORML

Though most of the studies cited by 4AutoinsuranceQuote.org suggest that marijuana’s impairing effects are minimal, other studies cast doubt on the safety of driving while high. Canadian researchers have recently concluded that smoking pot within three hours of driving nearly doubles the risk of a vehicle collision.

“The real takeaway shouldn’t be that cannabis makes one a safer driver, but that the changes in psychomotor performance are very different with cannabis than with alcohol,” said Armentano.

Impairment Inequalities

The complex effects of marijuana on driving ability make it difficult for states to develop marijuana DUI laws that are effective, fair and sensible. Some lawmakers believe that marijuana DUIs should be handled just like alcohol DUIs, in which blood tests are used to determine whether a driver is legally impaired. But blood samples containing THC, the psychoactive compound found in pot, do not necessarily indicate impairment the way samples containing alcohol do.

While peak blood alcohol content correlates nicely with peak levels of impairment, THC in the blood peaks within a few minutes of using marijuana, long before the drug’s strongest impairing effects set in. And depending on how often a driver uses pot, measurable levels of THC in blood can be found days later, even while the driver is completely sober.

But that hasn’t stopped researchers from trying to draw such a connection. A 2007 study found that a THC concentration of 10 nanograms/mililiter — a level sufficient to prove DUI in several states — is not associated with elevated accident risk. Concentrations between 7 and 10 ng/ml were correlated with impairment levels comparable to blood alcohol concentrations of .05%, which is well under the legal limit for alcohol DUI.

Altered States

Even though some studies suggest driving high isn’t dangerous, depending on where you drive, the legal risk can be undeniable. In most states, prosecutors must prove that a driver is actually impaired to secure a marijuana DUI conviction. But some states have per se DUI laws, meaning that drivers may be legally impaired by having specific concentrations of drugs or drug byproducts in their bodily fluids. In a few of these states, zero-tolerance standards prohibit drivers from having any measurable amount of these substances in their systems.

States with zero-tolerance standards for marijuana byproducts, called metabolites, pose particular problems for pot enthusiasts. Metabolites themselves cannot cause impairment; they are the non-psychoactive compounds created when the body processes THC. But they can remain detectable in urine for days after smoking pot, and even for weeks among heavy users.

Arizona, Delaware, Illinois, Indiana, Iowa, Rhode Island and Utah all maintain zero-tolerance standards for THC and its metabolites in blood and urine. The only exceptions are for medical marijuana patients in Arizona and Rhode Island who can legally drive with metabolites in their system, but not THC. Michigan and Wisconsin have zero-tolerance standards for THC, but exclude metabolites for all drivers.

Three other zero-tolerance states — Minnesota, North Carolina and Virginia — have specifically excluded marijuana and its metabolites from their drugged driving laws. In South Dakota, you can be found guilty of DUI solely for testing positive for THC or its metabolites only if you are under 21.

Nevada, Ohio and Pennsylvania are per se DUI states with specific limits for THC and metabolite concentrations. However, in Pennsylvania, the limit for THC or its metabolites is 1 ng/ml, which is effectively a zero-tolerance standard.

Marijuana users may also want to keep an eye on current efforts to institute per se standards in California and Colorado. A bill introduced in California aims to establish a zero-tolerance law, and another in Colorado is designed to set the THC blood limit at 5 ng/ml.

The Times They Are a-Changin’

Marijuana law reformists can take some solace in court decisions that challenge per se standards, like a 1999 Georgia Supreme Court case that found the state’s zero-tolerance statute unconstitutional. In this case, Everette Love was charged with DUI after an officer who stopped him for speeding smelled marijuana emanating from his vehicle. But after multiple appeals, the state’s highest court found that Georgia’s per se law unconstitutionally discriminated against sober drivers who tested positive for THC and its metabolites, as well as marijuana users who lacked the protection of a medical marijuana prescription.

“There are legal uses for marijuana and there are illegal uses, but there’s no way to distinguish between the two with a specimen test,” said Creal. “This is ultimately what the court found violated the equal protection clause.”

Still, those who drive with detectable traces of marijuana in their systems could find themselves vulnerable to additional charges that can amount to harsher penalties than a DUI alone.

“There are technically instances in which people can be charged with drug possession by consumption,” said Creal.

With an ever-changing state-by-state landscape of marijuana DUI laws, it can be challenging to determine where your defense stands. Check the DUI and DWI section of Lawyers.com for more information and to locate an attorney who can evaluate your case.

Do you agree or disagree with the studies claiming driving high on marijuana is less dangerous than driving drunk? Please leave a comment below.